The invention relates to a transmission, such as a continuously variable cone-pulley belt transmission that is arranged in the torque flow path of a motor vehicle between a it prime mover unit and at least one wheel and has an input shaft, an output shaft, a start-up element, and a direction-reversing element.
As a rule, transmissions of this kind are very compact in the axial direction, because the two pairs of pulley discs use up only a small amount of axial space. In the radial direction, however, the same transmissions are very large and require a great amount of space.
Transmissions, including continuously variable transmissions such as cone-pulley belt transmissions, e.g., for vehicles with a front-mounted engine and rear-wheel drive, must be designed with a very narrow profile so that they require only a small amount of space, because the drive-shaft tunnel of these vehicles is normally very narrow and constrained. Any space savings made by reducing the cross-sectional profile of the drive-shaft tunnel will be to the benefit of the interior space of the vehicle, which is a particularly desirable advantage.
It is therefore the object of the present invention to provide a transmission that has compact dimensions in the radial direction in relation to the drive shaft and incorporates improvements in design, function, and manufacturing cost.
The invention meets the foregoing objective in a transmission, such as a continuously variable cone-pulley belt transmission, that is arranged in the torque flow path of a motor vehicle between a prime mover unit and at least one wheel. The transmission has an input shaft, an output shaft, a start-up element, a direction-reversing element, a first pair of conical discs with an axially fixed conical disc and an axially movable conical disc, a second pair of conical discs with an axially fixed conical disc and an axially movable conical disc, an endless flexible chain belt to transmit torque between the first and second cone-disc pairs, a torque sensor, and actuators to effect axial movement of the movable conical discs. According to the invention, the objective stated above is met by the following arrangement of the elements in the torque-flow path, wherein:
in the sequence of the torque-flow path, the start-up element is arranged at some point after the input shaft, where the input side of the start-up element is connected to the input shaft and the output side of the start-up ico element is coaxial to the input shaft,
a gear stage is arranged between the output of the start-up element and the torque sensor,
the torque sensor and the first pair of conical discs are arranged coaxially on a first shaft,
the second pair of conical discs is arranged on a second shaft that is connected through a gear stage to the direction-reversing element,
the direction-reversing element is coaxial with the output shaft of the transmission.
Also advantageous is an arrangement of the elements in the torque-flow path, wherein:
in the sequence of the torque-flow path, the start-up element is arranged at some point after the input shaft, where the input side of the start-up element is connected to the input shaft and the output side of the start-up element is coaxial to the input shaft,
the torque sensor is arranged in sequence after the output side of the startup element,
the torque sensor and the first pair of conical discs are arranged coaxially on a first shaft,
the second pair of conical discs is arranged on a second shaft, with the direction-reversing element being arranged in the torque flow path at a point after the second shaft,
the direction-reversing element is arranged coaxially in relation to the output shaft of the transmission.
It is further practical if the start-up element and the first pair of conical discs are arranged to be coaxial.
It is likewise advantageous if the start-up element and a shaft of the first cone-disc pair are offset in relation to each other, with torque being transmitted from one to the other by means of a gear stage such as, e.g., a set of spur gears.
Furthermore, it is especially practical if the second pair of conical discs is arranged to be coaxial in relation to the output shaft.
It is likewise beneficial if the second pair of conical discs is offset against the output shaft, with torque being transmitted from one to the other by means of a gear stage.
It is particularly advantageous if in the first cone-disc pair, the axially movable disc is the one nearer to the input shaft.
It can also be advantageous if in the first cone-disc pair, the axially movable disc is the one nearer to the output shaft.
It is practical if in the second cone-disc pair, the axially movable disc is the one nearer to the input shaft.
In another embodiment, it is advantageous if in the second cone-disc pair, the axially movable disc is the one nearer to the output shaft.
In an advantageous embodiment of the invention, it is practical if the shaft of the first pair of conical discs is arranged above the input shaft. In another embodiment, it is practical if the shaft of the first pair of conical discs is arranged below the input shaft.
It is further advantageous, if the shaft of the second cone-disc pair is arranged above the input shaft.
It is likewise practical if the shaft of the second cone-disc pair is arranged below the input shaft. This allows space to be saved.
In an advantageous arrangement, space is saved if the shafts of the first and second pairs of conical discs are arranged to the side of the input shaft, as seen in an axial direction.
Likewise, it is advantageous if the shafts of the first and second pairs of conical discs as well as the input and output shafts lie in one plane.
It is particularly advantageous and space-saving, if the output shaft is arranged to be concentric with the input shaft.
Furthermore, it is particularly advantageous and space-saving, if the output shaft is arranged to be coaxial with the input shaft.
In an embodiment according to the invention, it is practical if the start-up element is a hydrodynamic torque converter with or without a converter-bypass clutch.
In another embodiment, it is practical if the start-up element is a friction clutch such as a dry-running single-disc clutch, or a wet-running laminar-disc clutch. Thus, the friction clutch can be a laminar clutch running in oil with at least one laminar disc. Likewise, the friction clutch can be configured as a dry friction clutch with one or more clutch discs.
It is further practical, if the direction-reversing element, such as a reverse-gear stage, has two clutches and a planetary gear set. In an arrangement of this kind, the clutches can also work, e.g., as brakes that engage a stationary element.
It is advantageous, if the start-up element and the direction-reversing element are configured as one modular unit.
It can further be practical, if the start-up element and the direction-reversing element are configured as one modular unit and are arranged ahead of the first cone-disc pair in the torque flow path.
It is likewise practical if the start-up element and the direction-reversing element are configured as one modular unit and are arranged after the second cone-disc pair in the torque flow path.
It is advantageous, if the axes of rotation of the pairs of conical discs are arranged parallel to each other.
It is likewise advantageous, if the axes of rotation of the input shaft and the output shaft are arranged parallel to each other and to the axis of the crankshaft.
According to a concept of the invention, it is advantageous if the actuator means include two piston/cylinder units for the pressure-actuated position-setting of the axially movable conical discs, with one piston/cylinder unit per cone-disc pair serving to set the transmission ratio and a second piston/cylinder unit per cone-disc pair serving to set the gripping pressure of the discs against the chain-belt.
In another embodiment of the invention, it is practical if the torque sensor within the transmission is omitted.
The invention further relates to a transmission, such as a continuously variable cone-pulley-belt-drive transmission, with the advantageous feature that the transmission has a transmission housing made of a foamed material. According to the invention, this will save weight as well as cost because the weight reduction will lead to lower fuel consumption. In addition to protecting the environment, this also translates into a cost advantage.
It is particularly practical if the transmission is made of foamed metal, e.g., aluminum, magnesium, or another light metal.
In accordance with a further inventive concept, it is also practical in a transmission if the transmission housing has hollow spaces that are at least partially filled with a foamed material.
In the embodiment just described, it is advantageous if the foamed material is aluminum, magnesium, or another light metal.
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.